1. Field of the Invention.
This invention relates to material processing and more specifically to the processing of roadways; mine tunnel roofs, side walls, floors and forward faces; and other surfaces where portable machines perturb such surfaces using tool bits or other cutting tools extending outwardly from the cylindrical surfaces of rotating drums.
2. Description of the Prior Art.
It is well known to mill road surfaces using a motor driven rotatable roller equipped with hard-metal cutters. Such rollers are moved horizontally relative to the road surface while the roller is rotated to bring the hard-metal cutters in contact with the surface of the roadway to be milled. See U.S. Pat. No. 3,975,055 granted to Wirtgen on Aug. 17, 1976.
It is well established that the cooling of such hard-metal cutters to dissipate the heat generated by the cutting will greatly increase the useful working life of those cutters.
Before the present invention, this cooling was sometimes attempted by encompassing the motor driven rotatable roller in a hood such as is seen in the Bros Brochure 7WG81. Copious quantities of water coolant were then sprayed out of a spray bar and down into the top of the hood. Water coolant tankers had to run alongside of or ahead of the actual milling machines themselves to provide sufficient water for sustained operation. Something of the arrangement used can be understood from a consideration of four-page BOMAG Brochure CGE-5439-2 where a similar system is disclosed for adding water and lime slurry to the cylindrical roller and the materials being cut out of the roadway by the roller.
A major difficulty with the process of cooling the cutting tools by spraying water on the outside of the drum is that this water is necessarily picked up by the roadway materials which have been cut out by the cutting tools. To get sufficient cooling action, many, many times as much water as is theoretically needed must be sprayed onto the drum as most of the water is immediately soaked up by the roadway cuttings, and so is not available for cooling the cutting tools. This necessitates the use of such large quantities of water that water supply trucks running alongside of or ahead of the milling apparatus are a necessity.
Once the water has served its purpose, and the machine moves on, the water is left in the processed roadway materials, thus "polluting" the final mix with water which does not enhance, but can greatly retard, the further processing.
What was needed before the present invention was some way of cooling tungsten carbide tipped steel cutting tools among others as the supporting roller rotated to bring those tools in contact with the roadway surface being processed without using appreciably more water or other coolant than was actually necessary to perform the cooling.